1. Field of the Invention
The invention relates to rotary machine and gas turbine engine rotor and stator airfoils and, particularly, to composite rotors and stator airfoils.
2. Description of Related Art
Aircraft turbine engines and other typed of rotary machines include a stationary and rotating airfoils which channel an airflow downstream. As a result, a wake flow may be generated and channeled downstream where it may impinge against an object downstream from the airfoils. Wake flow impingement may generate undesirable noise and/or aeromechanical loading. Unwanted noise may be generated by either the upstream rotating airfoil wake impinging on a stator or rotor component downstream from the rotating airfoil, or the upstream stator airfoil wake impinging on a rotating airfoil downstream from the stator airfoil.
The generation of such wake flow may result in a loss of engine performance and engine efficiency. Reduction of the amplitude of the wake flow may reduce the noise and the aeromechanical loading generated when the wake impinges against a downstream object. An airfoil designed to reduce the amplitude and/or coherence of the wake flow, the noise, and the aeromechanical loading is disclosed in U.S. Pat. No. 8,083,487, entitled “AIRFOILS FOR USE IN ROTARY MACHINES AND METHOD FOR FABRICATING SAME”, by Trevor Howard Wood et al., which issued Dec. 27, 2011 and is incorporated herein by reference. The airfoil includes suction and pressure sides coupled together at a leading edge and a trailing, wherein the airfoil includes a plurality of first and second chord sections each extending between the trailing and leading edges, wherein at least one of the first chord sections extends outward from the pressure side of the airfoil at the trailing edge, and at least one of the second chord sections extends outward from the suction side of the airfoil at the trailing edge.
Particular embodiments of the airfoil are wavy or crenelated airfoils.
Composite fan blades have been developed for aircraft gas turbine engines to reduce weight and cost, particularly for blades in larger engines. A large engine composite wide chord fan blades offer a significant weight savings over a large engine having standard chorded fan blades. The term composite as used herein may be defined as a material containing a reinforcement such as fibers or particles supported in a binder or matrix material. Composites include metallic and non-metallic composites. One particularly useful embodiment for fan composite fan blades is made of a unidirectional tape material and an epoxy resin matrix. The composite fan blade and other airfoils disclosed herein may include composite materials of the non-metallic type made of a material containing a fiber such as a carbonaceous, silica, metal, metal oxide, or ceramic fiber embedded in a resin material such as Epoxy, Polyimides (commercially known as PMR15), Bismaleimides (BMI), Polyetheretherketone (PEEK), etc. A more particular material includes fibers unidirectionally aligned into a tape that is impregnated with a resin, formed into a part shape, and cured via an autoclaving process or press molding to form a light-weight, stiff, relatively homogeneous article having laminates within.
It is highly desirable to provide light-weight and strong aircraft gas turbine engine fan blades that also reduce the amplitude of wake flow, noise, and aeromechanical loading.